Lichens are consortiums consisting of some kinds of fungi and algae and belong to a group of plants which occupy a botanically specific position. Metabolites of these lichens, that is, lichen components are quite different from components of other various higher or lower plants and they belong to a botanically specific class. They are definitely classified by Asahina et al. (See Asahina and Shibata, "Chemistry of Lichen Components," published by Kawade Shobo, 1948.)
It has been considered that a physiological significance of lichen components exists in defense against attack of microorganisms or insect plague because lichens grow slowly, or it exists in defense against ultraviolet rays because they grow in the sunshine, different from other fungi. Therefore, lichen components have hitherto been used for applications which came out of these functions. Examples thereof include dyes, antibiotics, flavors and the like. However, in fact, little study has been made on a pharmacological effect of these lichen components.
Lichens grow slowly and, further, their growth is liable to be restricted by natural environments (e.g. season, climate, temperature, latitude, etc.) as well as artificial environments (e.g. sulphur dioxide gas concentration, smoke concentration, etc.). Therefore, it is extremely difficult to culture lichens, which results in no success. Further, as is often the case in lichens, there the two are similar in form, but totally different in component. Therefore, selection of raw materials requires great skill and it is difficult to collect from nature. In order to obtain a method for producing lichen components, a study on cell culture has recently been made. Since lichens grow rapidly by cell culture in comparison with natural culture which needs a growth period of years or months. Therefore, it is possible to produce a subjective component in a short period of time. Further, different from a natural culture, there are advantages that it is not influenced by the weather and need not a lot of persons on collection and, further, it is possible to conduct planned production on an industrial scale. As a method comprising for culturing lichen cultured cells to be extracted and collecting a lichen component from the cells, for example, there is the present inventor's application (Japanese Patent application No. 58-56689); however, it was not known whether lichen cultured cells produce a melanin production inhibitor or not.
A melanin pigment which causes coloring of skin is produced at a melanin production granule in melanocyte between cutical and corium and melanin thus produced diffuses into adjacent cells. At present, a biochemical reaction in melanocyte is assumed to be as follows. One of essential amino acids, that is, tyrosine converts into dopa, further into dopaquinone due to an action of tyrosinase, which changes into black melanin through red pigment or colorless pigment due to enzymatic or nonenzymatic oxidation action. This process is a production process of melanin pigment. Accordingly, it is considered that production of melanin can be depressed by depressing biosynthesis of tyrosinase or depressing an action of tyrosinase as the first stage of the reaction, or by reducing quinones at an intermediate stage. Accordingly, facial effect can be obtained by formulating a substance which depresses biosynthesis of tyrosinase, or depresses or inhibits the action of tyrosinase.
It has been suggested that the certain substances produce the above mentioned depression. These include substances which bond with copper as an active center of tyrosinase (e.g. thiourea, cysteine, kojic acid, etc.) substances which can become a competitive substance with tyrosine as a substrate of tyrosinase (e.g. N-acetyltyrosine, .gamma.-pyrone, hinokitiol, etc.), substances which elongate an induction period of the reaction of tyrosinase and substrate (e.g. Tween 20, etc.), substances which selectively bond with o-dihydroxy group such as dopa (e.g. molybdenum ion, etc.), substances which bond with o-quinones (e.g. aniline, etc.), reductants for o-quinones (e.g. acorbic acid, hydroquinone and derivatives thereof, etc.) and the like.
Cosmetics wherein such melanin production inhibitors are formulated, however, are not satisfactory in view of toxicity, stability and influence due to functional group for human. Accordingly, the development of cosmetics containing stable melanin production inhibitors in high safety has been requested heretofore.
Under these circumstances, the present inventors have paid attention to cosmetics wherein natural products are formulated in view of safety. Further, the present inventors have intensively studied whether extracts of lichens which have ever been used as a crude drug can be used as cosmetics having excellent facial effect or not. As a result, it has been found that the production inhibitors extracted from lichen cultures, and the present invention has been completed.